Spicy food flavoured with hot chilli peppers contains a natural chemical ingredient that may lower blood pressure, according to a study on a strain of laboratory rats with hypertension.
Scientists have discovered that the long-term ingestion of capsaicin, the ingredient in chillies that makes them taste hot, can reduce blood pressure – at least in rats.
Previous studies have produced mixed results when it comes to finding a link between hot chillis and blood pressure, but this may be because they were carried out over relatively short time periods, the scientists said.
The study, published in the journal Cell Metabolism, suggests that capsaicin works by activating a special “channel” in the lining of the blood vessels called the transient receptor potential vanilloid 1 (TRPV1). When the channel is activated, it increases the production of nitric oxide in the blood vessels that is believed to protect against inflammation and other vascular problems.
The ingredient works by activating a receptor channel found in the lining of blood vessels. This leads to a rise in production of nitric oxide, a gaseous molecule known to protect blood vessels against inflammation and dysfunction.
The study was not the first to look for a molecular link between capsaicin and lower blood pressure, but earlier studies were based on acute or short-term exposure to the chemical, rather than long-term treatment with capsaicin on rodents with high blood pressure.
Researchers said further studies would be needed to see how many chillis would need to be eaten each day to have a positive impact on humans.
Professor Zhiming Zhu, who led the study, noted that hypertension affected more than 20 per cent of people in north-eastern china compared to 10 to 14 per cent in south-western China where the residents eat ‘hot and spicy foodswith a lot of chilli peppers.’
In the UK high blood pressure is thought to affect around one in three adults.
The common species of chili peppers are:
* Capsicum annuum, which includes many common varieties such as bell peppers, wax, cayenne, jalapeños, and the chiltepin
* Capsicum frutescens, which includes the chiles de árbol, malagueta, tabasco and Thai peppers
* Capsicum chinense, which includes the hottest peppers such as the naga, habanero, Datil and Scotch bonnet
* Capsicum pubescens, which includes the South American rocoto peppers
* Capsicum baccatum, which includes the South American aji peppers
The substances that give chili peppers their intensity when ingested or applied topically are capsaicin (8-methyl-N-vanillyl-6-nonenamide) and several related chemicals, collectively called capsaicinoids. Capsaicin is the primary ingredient in pepper spray.
When consumed, capsaicinoids bind with pain receptors in the mouth and throat that are responsible for sensing heat. Once activated by the capsaicinoids, these receptors send a message to the brain that the person has consumed something hot. The brain responds to the burning sensation by raising the heart rate, increasing perspiration and release of endorphins. A 2008 study reports that capsaicin alters how the body’s cells use energy produced by hydrolysis of ATP. In the normal hydrolysis the SERCA protein uses this energy to move calcium ions into the sarcoplasmic reticulum. When capsaicin is present, it alters the conformation of the SERCA, and thus reduces the ion movement; as a result the ATP energy (which would have been used to pump the ions) is instead released as heat.
The “heat” of chili peppers is measured in Scoville heat units (SHU), which is the number of times a chili extract must be diluted in water for it to lose its heat. Bell peppers rank at 0 SHU, New Mexico green chilis at about 1,500 SHU, jalapeños at 3,000–6,000 SHU, and habaneros at 300,000 SHU. The record for the hottest chili pepper was assigned by Guinness World Records to the naga jolokia (from northeastern India), measuring over 1,000,000 SHU. Pure capsaicin, which is a hydrophobic, colorless, odorless, and crystalline-to-waxy solid at room temperature, measures 16,000,000 SHU.